[Code Quality] Add antigravity engine to docs (engines.md, frontmatter-full.md) and schema examples

[github-actions]

Description

The antigravity engine is fully supported at runtime (pkg/workflow/engine_definition.go) and used in production workflows (.github/workflows/smoke-antigravity.md), but it is completely absent from user-facing documentation and schema examples:

• docs/src/content/docs/reference/engines.md lists only copilot, claude, codex, gemini, opencode, pi — no antigravity
• docs/src/content/docs/reference/frontmatter-full.md also omits antigravity from its built-in engine enum comments
• pkg/parser/schemas/main_workflow_schema.json engine examples (around lines 12488–12544) do not include antigravity

This creates false negatives for users who rely on documentation to discover valid engine IDs, while the runtime already accepts and validates antigravity.

Suggested Changes

1. Add an antigravity row to docs/src/content/docs/reference/engines.md alongside other built-in engines
2. Update the built-in engine ID list in docs/src/content/docs/reference/frontmatter-full.md to include antigravity
3. Add antigravity to engine examples/descriptions in pkg/parser/schemas/main_workflow_schema.json (around lines 12488–12568)
4. Optionally: add a regression test that compares registered engine IDs from runtime against the docs/schema to prevent future catalog drift

Files Affected

• docs/src/content/docs/reference/engines.md
• docs/src/content/docs/reference/frontmatter-full.md
• pkg/parser/schemas/main_workflow_schema.json

Success Criteria

• engines.md has an antigravity entry with description
• frontmatter-full.md built-in engine enum includes antigravity
• Schema examples include antigravity as a valid built-in engine ID
• All existing tests pass: make test-unit

Source

Extracted from Schema Consistency Check - 2026-07-26

Priority

Medium — documentation correctness; users cannot discover a supported feature from docs

🔍 Task mining by Discussion Task Miner - Code Quality Improvement Agent · sonnet46 · 41.7 AIC · ⌖ 8.4 AIC · ⊞ 7.2K · ◷

• expires on Jul 27, 2026, 11:11 AM UTC-08:00

[github-actions]

This issue was automatically closed because it expired on 2026-07-27T19:11:19.486Z.

Closed by Workflow